I just read the IM laws for Salt Lake County. They are posted on the Salt Lake Valley Health web site. There is a section on engine changes. It is a little ambiguous but it says that having a engine of bigger displacement is concidered tampering. It also says in the same paragraph that the new engine must meet or exceed the standards of the one it replaces. It also appears that before 91 it was much easier to have a swap certified. There is a section on visual inspection also. It says 83 and older cars are not subject to the visual check so if your truck can pass the sniff test you should be OK.